As devices and associated electronics are being pushed ever closer to their limits (both in terms of size and processing power), the underlying physics behind these technologies are being pushed to their absolute limit.
For the past four decades, the electronics industry has been driven by something called “Moore’s Law,” which is not so much a law, but more of an axiom. Simply put, it suggests that electronic devices double in speed and capability about every two years. And indeed, every year tech companies come up with newer, faster, smarter, and more novel electronic gadgets.
Specifically, Moore’s Law, as described by Intel cofounder and the Law’s namesake, Gordon Moore, is that “The number of transistors incorporated in a chip will approximately double every 24 months.” Transistors—miniscule electrical switches – are the fundamental building block that are at the heart of and drive every electronic device, machine, system, or platform on the planet. As they get increasingly smaller, they also become faster and consume less electricity to operate.
However, this exponential growth is not limitless. At some point, the underlying physics behind these components will simply reach its limit – beggining one of the biggest questions of the 21st century: How small can transistors truly become?
How close are we to the limit?
Currently, innovative companies like Intel are mass-producing transistors at approximately 14 nanometres across – just 14 times wider than the width of DNA molecules. They’re made of silicon, the second-most abundant material on our planet and silicon’s atomic size is about 0.2 nanometres.
Once at the nanoscale, the bizarre world of quantum mechanics takes a bigger hold. In this world, matter and energy behave in ways that seem counterintuitive and quantum physics is very different from classic physics – where particles cannot be observed without their behaviour being affected.
One particularly pertinent quantum effect is called electron tunnelling. Electron tunnelling, akin to teleportation, is when the material is very thin – the thickness of a single nanometre (about 10 atoms thick) – electrons can tunnel right through it as if it weren’t there at all. Though the electron doesn’t actually make a hole through the material, instead, the electron disappears from one side of the barrier and reappears on the other. Since transistors primarily function as gates that are meant to control the flow of electrons, this poses a problem.
If electrons can pass through a gate under any set of circumstances, there’s no way to control their flow, so the ultimate purpose of the device would be ineffective or not functional at all. With companies like Intel working on transistors that measure only 14 nanometres in width, it won’t be long before the oxide layer becomes too thin to act as a gate for electrons – using traditional transistors.
A transistor has three parts; much like a camera. First, information comes into the lens, equivalent to a transistor’s source. It then travels through a channel from the image sensor to the wires inside the camera. And lastly, the information is stored on the camera’s memory card, which is called a transistor’s “drain”—where the information ultimately resides.
Currently, this all occurs via movement of electrons within the device and to substitute light as the medium, photons need to be moved around instead. Subatomic particles like electrons and photons travel in a wave motion, vibrating up and down even as they move in one direction, where the length of each wave depends on what it’s traveling through.
In silicon, the most efficient wavelength for photons is 1.3 micrometres, but electrons in silicon are even smaller—with wavelengths 50 to 1,000 times shorter than photons. Though one would think that this would mean devices using photons would need to be larger, there are two key aspects that go against this:
- A photonic chip would only require a small number of light sources, generating photons which can then be directed around the chip.
- Light is much faster than electrons. On average photons travel about 20x faster than electrons in a chip. That would mean devices could see speed increases of up to 20x faster, a speed increase that would take about 17 years to achieve with current electronic technology.
A number of scientists and research groups have demonstrated significant progress toward photonic chips in recent years. Moreover, recent developments in nanostructures, metamaterials, and silicon technologies have expanded the range of possible functionalities for these highly integrated optical chips – leading to an exciting and ever changing landscape for the future of electronic technology.
Dylan, Consultant, Leyton UK